The invention relates to a method for weaving a double layer cloth and to uses of the method, in particular for manufacturing airbag cloths.
U.S. Pat. No. 5,651,395 describes methods for the manufacture of bags for airbags, with double layer cloths being produced for this manufacturing process. In cloths of this kind, two-layered regions can be distinguished from single-layer regions. The inflatable inner spaces of the bags are formed by the two-layered regions, which consist in each case of a lower and an upper cloth. In the single-layer regions, warp threads, which are located separately in the two-layer regions either in the upper or the lower cloth, are made to one another through technical binding measures to form a common partial cloth. The closed seams of the bags can be manufactured from the single-layer regions, which completely surround the two-layered ones.
High demands are placed on the quality of the double layer cloths, for example for airbags—i.e. on the so-called product rejection. The warp and weft threads must be uniformly and relatively densely arranged in the cloth. The deviation from a specified air permeability of the lower and the upper cloth respectively should be a minimum. The cloth layers must thus be as uniformly impermeable as possible. The threads used must be able to withstand high stresses in regard to tension and extension. The double layer cloth for airbags is a measured product, namely a cloth which is manufactured to an exact measure. On weaving machines which are equipped in the usual manner, the double layered nature has unfavorable effects on the product rejection when measured products are to be manufactured.
During the transport of the cloth by means of a drive roller (or a cloth draw-off beam) away from the location at which the weft threads are inserted and beaten up (beat-up edge, cloth edge), the cloth layers are mutually displaced, which leads to disadvantageous transverse folds. The non-uniform transport of the two layers arises in a so-called bar temple or spreader bar, which is usually used for the positioning of the beat-up edge and the spreading of the cloth. A spreader bar with left-hand/right-hand thread, which is arranged before the drive roller, additionally contributes to the formation of folds.
A method is also known from SU-A-1703731 by means of which the formation of folds could be prevented. In this method, however, needles are stuck into the cloth, which would impair the impermeability of the airbag.